1. Field of the Invention
The present invention relates generally to the field of magnetic read/write heads and magnetic data storage, and more particularly, to a thin film writer, and method of fabricating the same, for use in inductive read/write heads that utilizes a laminated flat top pole having a bottom shaper to control eddy currents and inefficiencies in high frequency applications.
2. Relevant Background
Data is stored on magnetic media by writing on the magnetic media using a write head. Magnetic media can be formed in any number of ways, such as tape, floppy diskette, and hard disk. Writing involves storing a data bit by utilizing magnetic flux to set the magnetic moment of a particular area on the magnetic media. The state of the magnetic moment is later read, using a read head, to retrieve the stored information.
Data density is determined by the amount of data stored on an area of magnetic media and depends on how much area must be allocated to each bit. Data on magnetic media is often stored in a line or track. Magnetic media often have multiple tracks. In the case of disks, the tracks are nested annular rings with more bits per track and more tracks per disk increasing data density. Data density or a real density, therefore, is determined by both the bit length and by the width of the bit. To decrease bit size, head size is decreased by fabricating thin film read and write heads.
Thin film write heads are typically formed by depositing and etching layers of magnetic, non-magnetic, dielectric, and electrically conductive materials to form the structures of the head, such as a core, a conductor winding, and upper and lower pole tips and yokes. Write heads typically do not contact the magnetic media but instead are separated from the magnetic media by a layer of air or air bearing. Magnetic flux generated between poles of the write head, e.g., on an air bearing surface (ABS), acts across the air bearing to change the magnetic moment of an area on the magnetic media.
Recently, the growth rate of a real density in hard disk drives has been over fifty percent per year. There are significant design and material processing challenges involved in reducing the size of writing heads to conform to the higher track and bit densities that have enabled a real density to grow so rapidly. Because output signal declines proportionally with reductions in track width, new materials with greater sensitivity to magnetic fields need to be developed.
In order for high moment material to be useful for write head applications, several requirements have to be met. The material must be magnetically soft with low coercivity value, and it also must have high permeability and low magnetostriction. As ever smaller structures must handle higher magnetic flux, the write head structures, and in particular the top pole or yoke and pole tips, become susceptible to saturation. As a result, it is necessary to form the pole structures of material with a sufficiently high magnetic moment to handle high flux density without saturating.
The rate or frequency that data is stored to the media is an important measure of the operational performance of the write head. One problem with operating at higher frequency is that the permeability of the material diminishes. As the magnetic flux changes, it generates a corresponding electrical field encircling the magnetic flux opposing the change. In an electrically conducting material, the induced electrical field generates current, referred to as eddy current, which in turn generates an opposing magnetic field. This not only limits flux switching time, but also causes saturation near the edge of the structure, thus lowering the permeability of the structure at high frequency. Laminating the top pole structure or yoke with a non-magnetic insulative material improves high frequency performance over conventional single layer structures. The insulative material reduces eddy currents in the structure, which can be a significant problem in higher frequency write heads. A drawback with this structure is that the non-magnetic laminating layers must be stopped short of the air bearing surface to allow flux to travel toward the write gap within the pole tip.
Hence, there remains a need for a write head or writer, and method of fabricating such as writer, with improved high frequency performance. Preferably, such a writer should address the need for reducing eddy current loss and maintaining flux conducting capability to achieve high writer efficiency while also being configured to support relatively simple fabrication that can be performed with enhanced process control.